1. Field of the Invention
The present invention relates to a glue wheel for use with a glue shoe in applying a pattern of cold glue to a glue flap or the like.
2. Brief Description of the Prior Art
In the manufacture of a cardboard or paperboard shipping container, glue is applied to a tab called a glue flap that projects from one of the outside panels of a box blank. After the glue is applied, the two outside panels are folded onto two inside panels to convert the box blank into a collapsed flat folded form. This operation is performed, usually at high speeds, in a folder-gluer machine. The flat folded form may thereafter be shipped to a customer for erection and filling with product to be shipped therein.
To create a strong container, the glue must be applied to the glue flap uniformly and in an effective amount. A glue unit with a glue shoe having an adjustable metering plate and a glue wheel as described in U.S. Pat. No. 5,443,683 to Garrett can be used to apply a uniform, controlled amount of glue to a glue flap.
The glue wheels described in U.S. Pat. No. 5,443,683 have a rim and an axis of rotation about a shaft. A plurality of grooves or the like are spaced, preferably uniformly, about the central portion of the rim and running transverse the axis of rotation of the glue wheel. The grooves are designed to accept a definite amount of glue for delivery of the glue in a predetermined pattern on the glue flap. The grooves are flanked with smooth side sections for sealing engagement with complementarily curved side walls of the glue shoe when the side walls of the glue shoe are spaced about 0.001 inch from the smooth side sections of the glue wheel. A metering plate is provided in the glue shoe that is movable towards and away from the glue shoe so that the bottom of the plate is between about 0.001 to about 0.016 inch from the wheel. The thickness of the glue applied by the glue wheel is controlled by the distance the plate is raised above the grooves in the glue shoe.
The glue typically used in a folder-gluer is a cold glue and is air dried. Cold glues have been reformulated to meet air quality standards and volatile organic compounds have been removed making them more difficult to handle. When the grooves are machined in the glue wheel described in U.S. Pat. No. 5,443,683, the crests between the grooves are wider along the smooth side sections. With cold glues presently available, a bead of dried glue tends to form along the smooth side sections as the glue is metered in a thin layer over the widened crests. Sometimes these beads flip off, ruining the piece that is being glued. In addition, because of the close tolerances between the glue shoe, metering plate and glue wheel in the glue unit described in U.S. Pat. No. 5,443,683, there is considerable drag on the glue wheel. It is also necessary that an operator have good mechanical skill in positioning the metering plate to obtain a desired glue pattern, a skill that a production worker may not have.
In view of the above, it is an object of the present invention to provide an improved glue wheel that minimizes the formation of a dried glue bead along the side edges of the wheel. It is another object to provide a glue wheel on which the glue shoe creates less drag. It is also an object to provide a glue wheel that makes it easier to set a glue pattern. Other objects and features of the invention will be in part apparent and in part pointed out hereinafter.
In accordance with the invention, a glue wheel for applying a glue pattern of cold glue to a receiving surface such as a glue flap has a hub with a central axis. The hub is adapted for rotation about the axis and has a rim with a plurality of spaced structures recessed in the rim that project outwardly. These recessed structures are flanked by smooth side sections for sealing engagement with a glue shoe. A circumferential groove passes through the recessed structures adjacent the smooth side sections.
In use, the glue is metered between and on the recessed structures by a glue wheel for application to a receiving surface in a desired glue pattern. The circumferential grooves substantially prevent the formation of a bead of dried glue on the recessed structures along the smooth side sections.
The invention summarized above comprises the constructions hereinafter described, the scope of the invention being indicated by the subjoined claims.